Effects of osmotic stress on Methanococcus thermolithotrophicus: 13C-edited 1H-NMR studies of osmolyte turnover

• Published in: Biochimica et biophysica acta Vol. 1427; no. 2; pp. 193 - 204
• Main Authors: Ciulla, Rose A, Roberts, Mary F
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 19.04.1999
• Subjects: Archaea; Carbon Isotopes; Formates - chemistry; In vivo nuclear magnetic resonance spectroscopy; Lysine - analogs & derivatives; Lysine - biosynthesis; Magnetic Resonance Spectroscopy; Methanococcus - chemistry; Methanococcus - drug effects; Methanococcus - growth & development; Methanogen; Osmolyte; Osmotic Pressure; Osmotic stress; Sodium Chloride - pharmacology; β-Amino acid; Osmolyte; Methanogen; In vivo nuclear magnetic resonance spectroscopy; Archaea; β-Amino acid; Osmotic stress
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/S0304-4165(99)00033-1

In vivo NMR studies of the thermophilic archaeon Methanococcus thermolithotrophicus, with sodium formate as the substrate for methanogenesis, were used to monitor formate utilization, methane production, and osmolyte pool synthesis and turnover under different conditions. The rate of formate conversion to CO 2 and H 2 decreased for cells adapted to higher external NaCl, consistent with the slower doubling times for cells adapted to high external NaCl. However, when cells grown at one NaCl concentration were resuspended at a different NaCl, formate utilization rates increased. Production of methane from 13C pools varied little with external NaCl in nonstressed culture, but showed larger changes when cells were osmotically shocked. In the absence of osmotic stress, all three solutes used for osmotic balance in these cells, l-α-glutamate, β-glutamate, and N ϵ-acetyl-β-lysine, had 13C turnover rates that increased with external NaCl concentration. Upon hyperosmotic stress, there was a net synthesis of α-glutamate (over a 30-min time-scale) with smaller amounts of β-glutamate and little if any of the zwitterion N ϵ-acetyl-β-lysine. This is a marked contrast to adapted growth in high NaCl where N ϵ-acetyl-β-lysine is the dominant osmolyte. Hypoosmotic shock selectively enhanced β-glutamate and N ϵ-acetyl-β-lysine turnover. These results are discussed in terms of the osmoadaptation strategies of M. thermolithotrophicus.